Shaft kilns



April 16, 1957 H. POOLE-.Y ETAL 2,788,951

SHAFT KILNS Filed Jan. 29, 1954 2 Sheets-Sheet 1 April 16, 1957 PooLEY ErAL SHAFT KILNS 2 Sheets-Sheet 2 Filed Jan. 29. 1954 SHAFT KILNS Henry Pooley, London, and Lione! Douglas Parker, Woking, England, assignors to Vickers-Armstrongs Limited, London, England, a British company Application January 29, 1954, Serial No. 407,058

Claims priority, application Great Britain February 3, 1953 Claims. (Cl. 263--29) This invention relates to shaft kilns for burning cement clinker, lime, or for the sintering of ores or for similar purposes.

Gas tired vertical shaft kilns in which the gas enters the kiln from side ports are known. Such kilns suffer the disadvantage that the heating gas is released directly into the material to be treated and combustion tends to be conned by the material to the periphery of the kiln. Consequently, uneven burning results due to the diniculty of transferring the heat from the periphery to the centre of the kiln. A further disadvantage lies in the fact that, due to the llame being entirely surrounded by materiai, local fusion of the material around the periphery of the kiln occurs, causing the downward ow of the material to be retarded. The high concentration of heat immediately :adjacent to the arched brick lined gas inlets, causes excessive deterioration of the tire-brick lining at the inlet points, necessitating frequent stoppages for repairing tne brick lining.

An oil tired shaft kiln has been proposed in which the oil for combustion passes down a central tiring pipe from the top of the kiln into a burning zone. In this case also combustion is localised and uneven burning results due to the diiculty of transferring the heat from the centre of the kiln to the periphery. The same disadvantages occur when a kiln is gas tired by a central rin-g pipe. The known kilns also suliier the disadvantage that the burning conditions cannot be observed.

It is an object of the invention to provide a centrally tired shaft kiln in which the disadvantages mentioned above are eliminated or minimised.

According to the inventionthere is provided a shaft kiln in which there is located a material deecting member, irmnediately beneath which a fuel burner is located for tiring the kiln, and in which the shaft converges downwardly to a reduced cross-section at about the region of the deecting member so that, when the kiln is in operation and material to be treated passes downwardly therethrough, a combustion chamber is formed defined by the detiecting member and the natural slope of the material therebeneath so that combustion occurs substantially over the entire reduced cross-section of the kiln.

For a better understanding of the invention and to show how the same may be carried into eect, reference will now be made to the accompanying drawings, in which:

Figure l is a sectional elevation of one constructional form of kiln,

Figure 2 is a sectional elevation of another constructional form of kiln,

Figure 3 is a fragmentary side elevation corresponding to Figure 2, and

Figure 4 is a fragmentary section of a modified form of kiln.

Referring now to the drawings, the constructional form of ldln shown in Figure l is provided with a feed portion generally indicated at l, and a lower portion, generally indicated at 2. The wall 3 of the portion l converges at 4 so that the lower portion 2 has a smaller Patented Apr. 16, 1957 diameter than the portion 1. An enclosed walkway 5 having a oor 6, extends through and across the feed portion 1 of the kiln. A firing pipe 7 passes through the tioor 6 into a combustion chamber 8, the walkway 5 accommodating the feed pipe for said firing pipe 7. The floor 6 is provided with peep holes 24 also extending into the combustion chamber so that the interior of the chamber 8 may be viewed. The combustion chamber 8 is deiined by a truste-conical cap body 9 acting as a material deliecting member and the surrounding material closing the open end thereof as shown.

Beneath the member 9 several arched openings 10 are formed to allow the material to be treated to enter the kiln portion 2 beneath the chamber 8.

A fan or blower 1l is provided beneath the kiln, which fan forces air upwardly through the kiln to a chimney 12. The kiln is also provided with a number of material discharge locks 13 so that the material can be withdrawn from the kiln without interfering with the circulation of the air.

When the kiln is in use, the raw materials are fed through a hopper 14 and the kiln is tired by means of gas, oil or powdered coal through the tiring pipe 7. The fuel is burnt in the combustion chamber and the heat is spread over the full cross-section of the kiln at the burning zone 1S. Thus, an equal distribution of heat is ensured, resulting in more stable conditions and better burning. The material passes downwardly through the kiln and is discharged through the lock system 13. The air supplied by the fan il passes upwardly through the kiln and initially serves to cool the material to be discharged from the kiln, and later passes upwardly from the combustion zone and thus serves to pre-heat the material fed to the feed end of the kiln. The kiln has the advantages that it can be tired with powdered coal, oil or gas and the amount of fuel can readily be controlled. vDue to the presence or" a combustion chamber, the llame and burning conditions are visible and as already stated there is better distribution of heat over the whole crosssection of the kiln.

In the other constructional form, corresponding parts will be designated by the same reference numerals. In the constructional form shown in Figure 2, the air circulation is modified. A fan l draws air from the cooling zone of the kiln through the ports 17 located in the lower portion of the kiln, and draws air into the kiln through adjustable air inlets UA located beneath the kiln. The air drawn from the kiln by the fan i6 is delivered'as combustion air to a pipe 1S surrounding the ice;

`tiring pipe 7 or delivers primary air to the pipe 18 and secondary air to ports 13A. A second fan 19 draws the combustion gases down the kiln through the ports 20 situated beneath the burning zone of the kiln and thus the iiarne, in this constructional form, is drawn downwardly. At the same time the fan i9 also draws a portion of the air from the cooling zone of the kiln through the ports 2li, such air entering the kiln through the adjustable cold air inlets 17A. The gases discharged by the fan 19 are delivered through a channel 2l into the pre-heating zone of the kiln above the combustion chamber and pass upwards to the chimney and thus preheat the material entering the kiln through the hopper 14.

The downward drawing of the llame has the advantage of preventing the fire brick arches surrounding the combustion chamber from becoming too hot. Adjustable cold air inlets 25 are also provided in the circulation of the fan i9 so that the temperature of the air handled by the fan and discharged into the pre-heating zone can be controlled to a certain extent. This kiln also has the advantage that powdered coal, oil or gas can be used and the amount of fuel is readily controlled. The llame and Y structional forms of kilns.

burning conditions 'are visible as in the previous construction.

The through walkway may be omitted in both con In that case, the tiring pipe 'can extend downwardly through the kiln Vfrom above the kiln as shown in Figure 4, and peep-holes 24 are then provided `as shown, The peep-holes 24 extend from the combustion through the wall 3 tothe outside of the kiln.

We claim:

1. A centrally tired shaft kiln through which the material to be treated passes downwardly, said shaft kiln comprising a vertical shaft Vhaving an upper part, a lower part of reduced cross-section relative to that of the upper 4part and a short throat part converging sharply toward the lower part and connecting said upper and lower parts, a frusto-conical cap body having a convex face Vand supported in the shaft with its convex face directed towards the upper end of the shaft, said cap body being located in spaced relation to the side walls of the shaft at the lower end of said upper part adjacent the junction of the latter with said throat where it acts 'to deflect the material passing downwardly through 'the shaft, a fuel burner with its tiring end extending into the cap body and arranged to introduce combustible fuel into the space under the cap body, feeding means located at the upper end of the shaft for supplying the material to be treated to the shaft, and discharging means located at the lower end of the shaft for discharging the treated material, said cap body and the deflected material therebeneath in said throat part of the shaft defining a combustion chamber e in the central portion of the shaft within the material passing downwardly therethrough, whereby said lower part of reduced cross-section constitutes a treatment zone receiving the material from directly below the combustion chamber.

2. A shaft kiln as claimed in claim 1, including wall elements extending upwardlyl from the lower part of the shaft through the tmoat and supporting said cap body,

said wall elements being spaced with respect to each other to provide conduit means through which the material to be treated descends from the upper part into the lower part of the shaft.

3. A shaft kiln as claimed in claim 1, further comprising an enclosed through-walkway extending across and through the upper part of the shaft at a location immediately above said cap body, said walkway accommodating part of the fuel burner.

4. A centrally fired shaft kiln through which the material to be treated passes downwardly, said shaft kiln Vcomprising a vertical shaft having an upper part, a lower part of reduced cross-section relative to that of the upper part and a short throat part converging sharply toward the lower part and connecting said upper and lower parts, a material-deecting member having a concave face and supported in the shaft with its concave face directed tomaterial-deflecting member and arranged to introduceV combustible fuel into the space under the material` deiiecting member, feeding means located at the upper end of the shaft for supplying `the material to be treated to the shaft, discharging means located at the lower end of the shaft yfor discharging the treated material, said material-detiecting member and the deflected material therebeneath in said throat part -of the shaft dening aY combustion chamber in the central portion of the shaft within the material passing downwardly therethrough, a first conduit means including a first blower supported outside the shaft, a rst conduit connecting the intake of said lirst blower to a middle portion of said lower part to draw air into the blower from the lower end of the shaft, a second conduit connecting the outlet ofthe first blower to said upper part to supply primary air to the latter, said second conduit enclosing at its upper end the tiring end of the burner to preheat the fuel therein and having a branch connection to the upper end of said lower part to supply secondary air thereto, a second conduit means including a second lower supported outside the shaft, a 4third conduit connecting the intake of said second blower to the shaft immediately above said first Vconduit to draw into the blower combustion gases pulled down the shaft and air from the lower end of the shaft, and a fourth conduit connecting the outlet of the second blower to the upper part of the shaft immediately above and around the material-deflecting member to preheat the material descending through the shaft into the combustion zone.

5. A kiln according to claim 4, further comprising valve means accommodated in the walls of said third conduit and extending therethrough to a location outside .the shaft, whereby atmospheric air can be directly introduced into said third conduit for controlling the tern- VVperatureV of the gases therein.

References Ctedrin the le of this patent UNlTED STATES PATENTS Great Britain Sept. 2, 1920 t En es 

